1. Field of the Invention
The present invention relates generally to medical devices and methods. More particularly, the present invention relates to methods and devices for accessing the pericardial space in a minimally invasive manner.
The human heart is enveloped within a tissue structure referred to as the pericardium. The pericardium includes two major portions. The portion of the pericardium which lies immediately over the surface of the heart is referred to as the visceral pericardium. The second portion is formed as a sac around the visceral pericardium and is referred to as the parietal pericardium. Normally, the visceral and parietal pericardia lie in close contact with each other and are separated only by a thin layer pericardial fluid. The space (really more of a potential space) between the visceral and parietal pericardia is referred to as the pericardial space.
Access to the pericardial space can be necessary or beneficial under a variety of circumstances. Open surgical access van be obtained via open sternotomy where the patient's sternum is divided and the parietal pericardium is exposed. Alternatively, the pericardial space can be approached from a skin incision made below the xiphoid through which the parietal pericardium is identified. Such approaches, however, are highly traumatic, requiring general anesthesia and useful only under compelling circumstances. Access to the pericardial space can also be achieved using a thoracoscopic approach. Under general anesthesia, the left lung is deflated after which multiple holes are made for the thoracoscope and various instruments. The pericardium is then entered using standard videoscopic techniques. The thoracoscopic approach typically requires the placement of a chest tube and admission to the hospital for the initial 1-2 post-operative days.
In patients who require drainage of a large pericardial effusion, a simple percutaneous approach can be used. Through a small (2-4 mm) cutaneous incision between the xiphoid and costal cartilage, a spinal needle (18-20 gauge) is advanced in a superior/posterior fashion. At appropriate intervals, the stylet is removed and fluid aspiration is attempted. If no fluid is obtained, the stylet is replaced and the needle advanced again. This cycle is repeated until fluid is aspirated. If the needle is advanced too far, the heart can be punctured and is why a large pericardial effusion must be present on ensure adequate separation of the visceral and parietal pericardia.
A minimally invasive method for accessing the pericardial space is described in U.S. Pat. No. 5,827,216 to Igo et al. A pericardiocentesis apparatus is introduced via a subxiphoid approach to the heart. A vacuum is applied at a distal end of the device to form a “bleb,” i.e., a locally expanded region in the pericardium. A needle can then be penetrated through the bleb, and the needle used for drawing fluids, delivering drugs, or the like. Although theoretically plausible, the ability to reliably maintain a seal against the pericardium can be problematic.
For these reasons, it would be desirable to provide additional and improved methods and apparatus for the minimally invasive access to a patient's pericardial space. The methods and devices should be suitable for a wide variety of minimally invasive approaches to the pericardium, including at least intercostal/transthoracic and subxiphoid approaches, and the like. The methods and devices should further provide for secure and stable capture of the parietal pericardium and permit the opening of a large space or volume between the parietal and visceral pericardia. Such access methods and apparatus should be useful for a wide variety of procedures to be performed in the pericardial space, including fluid withdrawal, drug delivery, diagnostic and therapeutic electrophysiology procedures, pacemaker lead implantation, defibrillator lead placement, transmysocardial revascularization, transmysocardial revascularization with drug delivery, placement of the left ventricular assist devices, placement of the arterial bypass graphs, in situ bypass, i.e., coronary artery-venous fistulae, placement of drug delivery depots, closure of the left arterial appendage, and the like. At least some of these objectives will be met by the invention described herein.
2. Description of the Background Art
U.S. Pat. No. 5,827,216, describes a pericardial access tube which draws a vacuum on the parietal pericardium as part of an access procedure, as discussed above. U.S. Pat. No. 5,071,428, describes a method for accessing the pericardial space for defibrillation lead implantation by grasping the parietal pericardium with forceps and cutting the pericardium with a scalpel. U.S. Pat. No. 4,281,659, describes a probe system having paired helical wires for securing the probe to a patient's skin. U.S. Pat. No. 4,164,943, describes a catheter anchor having multiple helical wires for securing the anchor to a patient's skin. U.S. Pat. No. 5,226,890, describes a trocar cannula anchor having a tapered thread for placement in a percutaneous tissue penetration. U.S. Pat. No. 5,332,398, describes and intramedullary catheter having a threaded end for implantation into a bone.